Additive agents are often added to thermoplastic and thermosetting resins to achieve the physical properties required for formed products. For example, in formed products such as films, a saturated or unsaturated higher fatty acid amide, a saturated or unsaturated alkylenebisamide, or a fatty acid monoglyceride is added to provide surface lubricity, and an inorganic fine powder, for example, silica, zeolite, talc, calcium carbonate, or diatomaceous earth is added as an anti-blocking agent (hereinafter referred to as an AB agent) to prevent blocking. The inorganic fine powder is combined with the additive agent for providing surface lubricity.
In order to provide surface lubricity, however, a large amount of fatty acid amide must be added. In this case, in extrusion molding of a pelletized resin, a fatty acid amide in a resin has a lower melting point than the resin and therefore melts faster than the resin in an extruder cylinder heated to a high temperature, causing a phenomenon (called discharge pulsation or surging) in which resin pellets still in a solid state slip in the extruder and are not properly conveyed. A fatty acid amide having a lower molecular weight than a resin also causes problems of oily smoke and malodor at high temperatures. Furthermore, there is another problem of bleedout of the additive agent in a formed product.
An increase in the amount of AB agent, such as silica, added to a resin results in excessive bleeding of the AB agent over time or in high-temperature environments, causing deterioration in transparency. The amount of AB agent is therefore within the bounds of not causing deterioration in the transparency of a formed product. Thus, sufficient anti-blocking effects have not been achieved.
Thus, there is a demand for a resin composition that can solve these problems and has a high anti-blocking effect and excellent mold releasability of a formed product.
To obtain a pellet and a masterbatch by adding an additive to thermoplastic resins or thermosetting resins involves melt-kneading. The melt-kneading needs to be carried out with viscosities of both the resins and the additive being controlled so as to fall within a certain range and the melt-kneading temperature maintained at not more than temperature causing resin decomposition so as to inhibit the resin decomposition.
However, it may be difficult to carry out the melt-kneading the resins at temperature of not more than the temperature causing resin decomposition. In particular, some rubber resins having high adhesion, which are thermoplastic elastomers, may need to be kneaded at increased pressure, kneaded for plural times or kneaded at high temperature. The melt-kneading under such conditions may lead to thermoplastic elastomers having deteriorated properties such as decreased molecular weight caused by the resin decomposition. Thus, the addition of an additive to the thermoplastic elastomers has made the equipment and technique necessary for the melt-kneading special, compared with common thermoplastic resins. In addition, the difficulty in the processing of thermoplastic elastomers having particularly high adhesion, i.e., high adhesion and stickiness of the thermoplastic elastomers to a metal roll and a mold, makes kneading time longer and pollutes the mold, and thus leads to problems associated with decreased efficiency of production. Therefore, it has been desired to improve the processing in adding an additive to thermoplastic elastomers.
In recent years, propylene elastomers mainly composed of propylene have been known as soft polyolefin materials that are highly flexible, heat resistant, and transparent, as well as highly environmentally suitable and hygienic (Patent Documents 4 and 5). Unlike conventional olefin elastomers, such propylene elastomers have high transparency, heat resistance (high softening temperature), and scratch resistance and are therefore intended to broaden their product range to a wide variety of uses, such as electric/electronic device components, industrial materials, furniture, stationery, commodities and miscellaneous articles, containers and packages, toys, recreational equipment, and medical supplies. However, the stickiness of a material sometimes causes problems, thus limiting applications of the material.
Known methods for reducing the stickiness of materials involve the addition of slip agents (lubricants). For example, Patent Document 6 specifically discloses a technique of adding a higher fatty acid amide or a higher fatty acid ester to a propylene elastomer.
However, such a slip agent (lubricant) sometimes migrates to the surface of a product, causing a problem of whitening. Another problem is that a higher fatty acid amide or a higher fatty acid ester can be eluted into an alcohol and therefore cannot be used in products that are to be in contact with the alcohol.
In order to avoid such problems, a known technique involves the addition of a wax containing a low-molecular-weight polyolefin. While such a wax is known to be a polypropylene wax or a polyethylene wax, the effects of the wax greatly depend on the compatibility between the wax and a propylene elastomer. For example, because a polyethylene wax lacks compatibility with a propylene elastomer, a product containing these components may have very low transparency. On the other hand, because a polypropylene wax has excellent compatibility with a propylene elastomer, the wax component is not effectively localized in the vicinity of the surface and is likely to produce insufficient stickiness-reducing effects. Thus, there is a demand for a wax having moderate compatibility with a propylene elastomer.
Olefin polymers containing 4-methyl-1-pentene (hereinafter also referred to as 4-methyl-1-pentene polymers) have been used as resins having high transparency, gas permeability, chemical resistance, and releasability, as well as high heat resistance, in various fields, such as medical devices, heat-resistant wires, heat-proof dishes, and releasing materials. In particular, low-molecular-weight 4-methyl-1-pentene polymers have excellent mold releasability.
In general, 4-methyl-1-pentene polymers are produced in the presence of a catalyst composed of a transition metal compound and an organic aluminum compound, that is, a Ziegler catalyst (Patent Document 7). However, a polymer produced in the presence of a Ziegler catalyst has a nonuniform composition of a molecular weight of the polymer and a high proportion of a low-molecular region in a molecular weight distribution, possibly causing a problem of stickiness.
In the meanwhile, a 4-methyl-1-pentene polymer produced in the presence of a metallocene catalyst has been reported (Patent Document 8). The 4-methyl-1-pentene polymer has a uniform molecular weight and composition and also has a high molecular weight for the purpose of improving the balance of various physical properties, for example, thermal properties, such as heat resistance, and dynamic properties.
A low-molecular-weight 4-methyl-1-pentene polymer can be produced by the thermal decomposition of a high-molecular-weight 4-methyl-1-pentene polymer (Patent Document 9). However, such a low-molecular-weight 4-methyl-1-pentene polymer has a wide molecular weight distribution and contains a component having low stereoregularity, thus causing problems of blocking and stickiness.
Thus, there is a demand for a 4-methyl-1-pentene polymer having a low molecular weight and a uniform composition of a molecular weight of the polymer.